The goal of the present study is to evaluate the efficacy and durability of benefits of repetitive Transcranial Magnetic Stimulation (rTMS) as a promising non-invasive therapeutic treatment for executive function deficits reported in Veterans with mild to moderate Traumatic Brain Injury (TBI) patients. Although much progress has been made towards understanding the various deficits following TBI, progress has yet to be made towards identifying and assessing therapeutic treatment options that are responsive to TBI symptoms. Many returning OEF/OIF Veterans with concussion histories report cognitive symptoms that may last for months or years, and affect every day function. Symptoms faced by Veterans with mild to moderate TBI include executive function deficits such as impaired attention (including shifting sets), verbal fluency, poor planning, reduced working memory, and mental flexibility. The primary objective is to assess the efficacy of rTMS in Veterans with mild to moderate TBI in improving executive functioning. A recent VA study reported improvements in PTSD and related symptoms in Veterans with PTSD who received rTMS (Watts et al., 2012). Repetitive TMS is a method of delivering therapeutic, non-invasive brain stimulation that is currently being used at the VA Palo Alto and Stanford University in a number of clinical trials. For this pilot study we propose to enroll 40 Veterans diagnosed with mild to moderate TBI (age range 20-65). Inclusion Criteria: mild and moderate TBI will be defined as: post-traumatic amnesia (PTA < 1 day for mild; 1 day> x < 7days for moderate). Because of the extensively documented co-occurrence of TBI with PTSD, (Veterans with TBI with and without PTSD will be enrolled). PTSD will be assessed using standard clinical measures. Exclusionary criteria: patients will be screened for TMS and MRI safety. The duration of the study will be two years, with a 1.5 year enrollment period, and a final half-year of follow-up completion. Following a preliminary telephone screen, Veterans will be scheduled for onsite informed consent, screening, and baseline assessments. Using an electronic randomization form, participants will be enrolled into two groups: active rTMS or sham rTMS. As this is a double blind placebo controlled study, only the subject ID number is provided to the nurse administrating the rTMS treatment. After randomization, the rTMS nurse will test the motor threshold (MT) for rTMS. Each participant will be in the trial for a total of approximately (28) weeks: 1-2 weeks screening, (2) weeks acute treatment phase (including MRI pre and post rTMS) and 24 weeks (6 month) follow-up phase (with MRI, neuropsychological testing and self-report measures). Left Dorsolateral Prefrontal Cortex (DLPFC) will be the stimulation site as it is shown to be affective in treatment of depression and approved by FDA. All participants will receive a minimum of 20 treatments before being evaluated for change in executive function (primary outcome measure). The primary hypothesis is that Veterans receiving active rTMS will show improvement more than sham treated Veterans in (performance between baseline and last assessment of >1 SD on either the Trail Making Test part B, D-KEFS Verbal Fluency and/or D-KEFS Color-Word Interference Test). Additional analysis will include: Sustained Improvement on executive function composite score; secondary consequences of TBI scores on Quality of Life (QOL) scale, moderators of response such as age, severity of symptoms at baseline, type of comorbidity (e.g., PTSD); and, functional brain activity changes with rTMS treatment. This pilot study will be one of the first to demonstrate rTMS as a treatment for executive function deficit in Veterans with mild to moderate TBI. Additionally, it would also report on the efficacy of using fMRI as a biomarker to capture this improvement in executive function.